SNMP is a protocol used to monitor network devices and their performance. It has three main components: managed devices that contain SNMP agents, the agents themselves that reside on devices, and network management stations that execute applications to monitor devices. There are three versions of SNMP - version 1 was the initial implementation, version 2 improved on security and performance, and version 3 focuses on authentication, privacy and access control to be considered the current standard.

1. How Simple Network
Management Protocol
Works
・What is SNMP
・Internet Network Management Architecture
・SNMP basic components
・Versions of SNMP

2. What is SNMP(Simple Network
Management Protocol)
Simple Network Management Protocol (SNMP) is a
component of the Internet Protocol Suite as defined by
the Internet Engineerring Task Force(IETF).
SNMP is used in network management systems to
monitor network-attached devices for conditions that
warrant administrative attention. It consists of a set of
standards for network management, including an
Application Layer protocol, a database schema, and a
set of data objects.

3. The internet network management
architecture
SNMP is part of the Internet network management
architecture. This architecture is based on the interaction of
many entities, as described in the following section.
• Agents
• Managed object
• Management information base (MIB)
• Syntax notation
• Structure of Management Information (SMI)
• Network management stations (NMSs)
• Parties
• Management protocol

4. SNMP basic components
An SNMP-managed network consists of three key
components:
1.Managed devices
A managed device is a network node that contains an
SNMP agent and that resides on a managed network.
2.Agents
An agent is a network-management software module
that resides in a managed device.
3.Network-management stations (NMSs)
A network management system (NMS) executes
applications that monitor and control managed devices.

5. Versions of SNMP
SNMP has three versions.
・Version1
SNMP version 1 is the initial implementation of the
SNMP protocol. SNMP version 1 operates over
protocols such as User Datagram Protocol, Internet
Protocol, OSI Connectionless Network Service,
AppleTalk Datagram-Delivery Protocol, and Novell
Internet Packet Exchange .
・Version2
SNMP version 2 revises version 1 and includes
improvements in the areas of performance, security,
confidentiality, and manager-to-manager
communications.
But, because new party-based security system in
version 2 is more complex, SNMP version 2 was not
widely accepted.
・Version3
SNMP version 3 provides three important services:
authentication, privacy and access control. SNMP
version 3 is defined as the current standard version of
SNMP by the IETF. So, the IETF considers earlier
versions as obsolete or historical.

6. References
・Wikipedia
http://en.wikipedia.org/wiki/Simple_Network_Manage
ment_Protocol
・Internet Architecture
http://www.soi.wide.ad.jp/class/20030002/slides/03/19.
html
・Javvin
http://www.javvin.com/protocolSNMP.html
・Adventnet
http://www.adventnet.com/products/javaagent/java_sn
mp_agent_ds.html